Diagnosis would be easier if you posted the entire test results and the type of test, but if they tested NOx it was probably a loaded test on a dyno.

NOx is produced by peak combustion temps, but should be fairly low if the 02 sensor and KE system are maintaining the proper stoichiometric mixture.

Retarding the timing reduces peak combution temperature, and there have been many discussions on replacing the resistor on these cars to alter the timing. I recall that removing the resistor and shorting the pins will result in the lowest spark advance.

Prior to having the car tested you should always be certain that it is fully warmed up and the converter is hot as possible. If the converter cools off too much is is not as effective, and this appears to be a problem with the 103 engines, but it usually results in excess HC.

Duke